5-Nitrobenzofurans

Abstract

The present invention relates to 5-nitrobenzofurans, to a process for preparing 5-nitrobenzofurans, and to 5-nitro-2,3-dihydrobenzofuran-3-ols, to a process for the preparation thereof and to intermediates.

1. At least one compound of the formula (II),                  
 
       wherein
 R 1  is hydrogen or C 1 –C 12 -alkyl, and 
 R 2  are in each case independently of one another: fluorine, chlorine, bromine, iodine, C 1 –C 12 -alkyl, C 1 –C 12 -alkoxy, hydroxyl, NR 3 R 4  or CONR 3 R 4 , where R 3  and R 4  are each, independently of one another, hydrogen or C 1 –C 12 -alkyl, or NR 3 R 4  as a whole is a cyclic amino radical having 4 to 12 carbon atoms, COO—(C 1 –C 12 -alkyl), —COO(C 4 –C 24 -aryl), —COO(C 5 –C 25 -arylalkyl), CO(C 1 –C 12 -alkyl), CO(C 4 –C 24 -aryl) or C 1 –C 12 -fluoroalkyl and 
 n is zero, one, two or three, or
 in the case where n is two or three it is possible for two adjacent R 2  substituents to be part of a fused ring system which in turn may optionally be substituted by the radicals mentioned above for R 2 . 
 
 
     
     
       2. 2-(n-Butyl)-5-nitro-2,3-dihydrobenzofuran-3-ol. 
     
     
       3. A process for preparing at least one compound of formula (I),                  
 
       in which
 R 1  is hydrogen or C 1 –C 12 -alkyl and R 2  are in each case independently:
 fluorine, chlorine, bromine, iodine, C 1 –C 12 -alkyl, C 1 –C 12 -alkoxy, hydroxyl, NR 3 R 4  or CONR 3 R 4 , where R 3  and R 4  are each, independently of one another, hydrogen or C 1 –C 12 -alkyl, or NR 3 R 4  as a whole is a cyclic amino radical having 4 to 12 carbon atoms COO-(C 1 –C 12 -alkyl), —COO(C 1 –C 24 -aryl), —COO(C 5 –C 25 -arylalkyl), CO(C 1 –C 12 -alkyl), CO(C 1 –C 24 -aryl) or C 1 –C 12 -fluoroalkyl and 
 
 is zero, one, two or three, or
 An in the case where n is two or three it is possible for two adjacent R 2  substituents to be part of a fused ring system which in turn may optionally be substituted by the radicals mentioned above for R 2    
 
 
       comprising converting by dehydration 
       of at least one compound of formula (II)                  
 in which R 1 , R 2  and n have the meaning under formula (I) 
 
       into at least one compound of formula (I);
 wherein 
 at least one compound of the formula (II) is or are obtained by reducing at least one compound of the formula (III)                  
 
 wherein R 1 , R 2  and n have the meaning specified under formula (I) as indicated above. 
 
     
     
       4. The process according to  claim 3 , wherein wherein at least one compound of the formula (III) is or are reduced by aluminium-hydrogen or boron-hydrogen compounds. 
     
     
       5. The process according to  claim 3 , at least one compound of the formula (III) are obtained by nitrating compounds of the formula (IV)                  
 
       in which R 1 , R 2  and n have the meanings specified under formula (I). 
     
     
       6. The process according to  claim 5 , wherein compounds of the formula (IV) are obtained by hydrolysing at least one compound of the formula (V)                  
 in which 
 R 1 , R 2  and n have the meaning specified under formula (I) in  claim 3 , and 
 R 7  is C 1 –C 12 -alkyl, C 5 –C 25 -arylalkyl, C 4 –C 24 -aryl or C 1 –C 12 -fluoroalkyl. 
 
     
     
       7. The process according to  claim 6 , wherein at least one compound of the formula (V) is or are obtained by cyclizing decarboxylation of compounds of the formula (VI),                  
 in which R 1 , R 2  and n have the meaning specified under formula (I) in  claim 3 , 
 in the presence of at least one compound of the formula (RIII)
   R 7 COR 8   (RIII) 
 
 in which 
 R 7  has the meaning specified under formula (V), and 
 R 8  is —O 2 CR 7 , hydroxyl or OM, where M is an alkaline earth metal or alkali metal. 
 
     
     
       8. The process according to  claim 7 , wherein at least one compound of the formula (VI) are obtained by hydrolysing at least one compound of the formula (VII)                  
 in which 
 R 1 , R 2  and n have the meaning specified under formula (I), and 
 R 9  and R 10  are each independently of one another hydrogen, C 1 –C 12 -alkyl, C 5 –C 25 -arylalkyl or C 4 –C 24 -aryl. 
 
     
     
       9. The process according to  claim 8 , wherein at least one compound formula (VII) are obtained by reacting at least one compound of the formula (VIII)                  
 in which 
 R 2  and n have the meaning specified under formula (I) in  claim 3  and 
 R 10  has the meaning specified under formula (VII), 
 with at least one compound formula (IX)                  
 
 in which 
 
       R 1  has the meanings specified under formula (I) in  claim 3 , and 
       R 9  has the meaning specified under formula (VII), and 
       X is chlorine, bromine, iodine or R 11 SO 3 — where 
       R 11  is C 1 –C 12 -alkyl, C 4 –C 24 -aryl, C 5 –C 25 -arylalkyl or C 1 –C 12 -fluoroalkyl. 
     
     
       10. The process according to  claim 7 , wherein at least one compound of formula (VI) are prepared by reacting at least one compound of formula (VIII) with at least one compound of formula (IX) in a one-pot reaction with hydrolysis of the ester functions taking place simultaneously.